The present invention relates to a cover for a standard container, said container having a substantially rectangular bottom with rounded corners and side walls that are flared upwards, the tops of the side walls delimiting a substantially rectangular opening with rounded corners, said cover being constituted by a plate made of a thermo-plastic material and provided with upper rib portions which project from its upper surface in a rectangular configuration with gaps and with lower rib portions which project from its lower surface in a substantially rectangular configuration to fit into the opening.
Such a cover is described in U.S. Pat. No. 2,695,115. The cover described in said patent is provided with two sets of lower ribs, the first of which fits inside the opening of the container and the second of which fits round the outside of the container. Further, the second set of lower ribs makes it difficult to lift the cover with one hand.
The set of upper ribs on the cover described in the above U.S. patent co-operates with a set of ribs located beneath another container.
Since the containers are flared, is not easy to arrange for the set of upper ribs on a cover to match both the set of ribs on the bottom of a second container and the set of lower ribs of an identical cover. In other words, it is difficult to ensure that a pile of identical covers will stack properly, if the covers are specifically designed for proper stacking of closed containers, and vice versa.
Further, the second set of lower ribs which project further than the first set of lower ribs interferes with proper nested stacking of the covers on one another.